Remote control system



Jan. 20, 1970 i B. o. VAN NESS 3,491,254

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Bradford 0. VanNess ATTYS.

United States Patent 3,491,254 REMOTE CONTROL SYSTEM Bradford 0. Van Ness, Scottsdale, Ariz., assignor to M0- torola, Inc., Franklin Park, 111., a corporation of Illinois Filed Sept. 2, 1966, Ser. No. 577,033 Int. Cl. H03k 17/02 U.S. Cl. 307-239 3 Claims ABSTRACT OF THE DISCLOSURE A system for controlling turn-on and turn-off of remotely located equipment is disclosed. The control system is responsive to a two tone audio signal. When demodulated at the telephone receiver, the relative timing of the two signals determines whether the equipment is to be deactivated or reactivated.

This invention relates generally to remote control systems, and particularly to those systems used to turn equipment on and off in response to a two-tone encoded signal.

In the remote control of equipment, such as gasoline dispensing units at retail service stations, it is desired that the gasoline pumps be turned off only under certain conditions (such as expired credit). To provide security in such a system, a coded signal is used to turn the pumps off, while no such security coding is usually required for turning the pump on. In situations other than retail service stations it may be desired to have a security code for turning the equipment on.

In the retail service station remote control systems, encoding used to turn the gasoline pumps otf may be used as a control on the credit of the operator. For example, gasoline storage tanks may be filled to capacity. By using a system of remotely controlling the gasoline pumps, the number of gallons permitted to be withdrawn by the operator can be manually or semi-automatically controlled such that the permitted withdrawal is a function of the established credit of the operator. For example, in a storage tank having a capacity of 10,000 gallons, it may be desired to permit the operator to withdraw only 2,000 gallons. When the 2,000 gallons have been withdrawn, the pumps are turned off. Such remote control is preferably provided over a community telephone system.

Accordingly it is an object of this invention to provide a remote control system utilizing a secure encoded signal for at least one operation to be controlled.

It is a further object of this invention to provide a simple and inexpensive decoding system for use in a remote control system which is utilized to turn equipment on and off.

It is another object of this invention to provide a remote control system using pulse duration and timing techniques for providing security to the remote control system.

Referring now to the accompanying drawing:

FIG. 1 is a block or flow diagram of an exemplary decoder constructed according to the subject invention.

FIG. 2 is a set of idealized wave forms used to de scribe the operation of the FIG. 1 embodiment.

FIG. 3 is a block diagram of an encoding unit used to provide coded signals to the FIG. 1 embodiment.

FIG. 4 is a combined schematic and block diagram of selected portions of the FIG. 1 embodiment.

A remote control system utilizing the teachings of this invention includes a code generation means at a central point which is selectively activated to provide certain codes to selected receiving stations. Usually a two-tone transmitter is used in connection with the encoder, with the tones applied over a telephone network to a selected receiver. The selected receiver demodulates the received tones and provides two contact closures or other switchable output signals corresponding to the presence or absence of the tones. Usually the tone transmitter and receiver units are provided by a telephone communications company. It also may take the form of parts of other equipment and operate by principles or methods other than audio tone signals.

The output of the tone receiver is provided to a decoding means, which includes the teachings of this invention. The receivers two switchable output signals are received by the decoding means which responds thereto to either connect or disconnect equipment from power.

According to the illustrated embodiment the first and second tones as demodulated by the tone receiver must occur in the following sequence to turn the equipment off. A first tone is transmitted during the entire operation. After the first tone has been transmitted a predetermined time, a delay circuit is activated to provide a pulse to set a monostable multivibrator. After the monostable multivibrator has been set, the second tone is then trans mitted. The second tone and the output signal of the monostable multivibrator are combined in a circuit which deactivates the equipment. The second tone transmission is stopped before the monostable multivibrator automatically resets itself. To activate equipment, both tones are simultaneously transmitted for a predetermined time.

Referring now to FIG. 1 input means 10 receives de modulated tone signals from a tone receiver (not shown), such as a data-phone, and provides two contact closures in switches or controls 12 and 14. When a first tone, labelled A, is received, contacts 12 are closed to provide voltage V over line 16 to actuate delay circuit 18. The receipt of a second tone Signal, labelled B, is indicated by the closure of contacts 14. The receipt of tone A and not tone B (AB) during a first time period up to. time pulse 22A is emitted, indicates that the equipment, later described, is to be turned off. The signal conditions AB (A and B) during the same time period indicates the equipment is to be turned on. In turning equipment on, voltage is supplied through closed contacts 12 and 14 thence over line 20 to inhibit the operation of delay circuit 18, as by clamping. That is, if both signals A and B are received prior to the expiration of delay circuit 18 delay period, the circuit is deactivated and emits no pulse, indicating equipment may be turned on. Only if tone signal A and not B (AB) occurs for a time exceeding the delay of circuit 18, an electrical impulse 22A (FIG. 2) will be emitted to set monostable multivibrator 24 to its active condition indicating equipment is to be turned off. i

The circuit response to AB and AB is now described. Monostable multivibrator 24 has two output leads, 26 and 28 respectively from opposite sides of the bistable circuit. Waves 26A and 28A (FIG. 2) represent the output signals of circuit 24 upon receipt of impulse 22A representing AB. Wave 26A normally is at a relatively high potential and upon receipt of the pulse 22A by circuit 24 immediately switches to an activating low potential indicating circuit 24 is in its active condition. Contrarywise, wave 28A normally is at its activating low potential and upon receipt of the pulse 22A immediately switches to a non-activating high potential. Wave 26A when at its activating potential indicates that equipment is to be turned olf and corresponds to the previously mentioned signal AB.

Dual-amplifier circuit 30 respectively receives signals 26A and 28A and supplies them respectively over lines 36 and 38 to relay 34 when and only when an enabling signal is received over line 32. The enabling signal must occur during time period 30A and 30B (FIG. 2) on line 32 and is voltage V passed by input means 10 when it receives both tones A and B (AB). This signal condition of two simultaneously received tones is the next step in the decoding cycle. The maximum duration of the simultaneous receipt of tones A and B is determined by monostable multivibrator 24, as will become apparent. Amplifier 30 responds to activating wave 26A and the line 32 enabling signal by providing an activating signal over line 36 to set relay 34 to an OFF indicating state. Relay 34 is of the polar magnetic latching type and needs only a momentary signal to set it from one state to the other. However, when monostable multivibrator 24 is providing an activating signal over line 28 (tone signals AB are being received) amplifier 30 jointly responds to such signals by supplying an activating signal on line 38 to switch relay 34 to its ON indicating condition.

Relay 34 indicates its ON indicating condition or state by closing contacts 40. Such an indication may be connected to an electric indicating circuit (not shown). Also, a set of C contacts are provided with a center arm 42 bearing against contact 44 when relay 34 is in the OFF state. Such contact closure connects voltage V to an indicator bulb 46 for indicating to the station operator that his pumps have been turned OFF. Arm 42 is disconnected from contact 48 and therefore disconnects enabling voltage V from equipment turn ON and OFF control 50, deactivating the pumps for preventing their usage. When relay 34 is activated to its ON state, contacts 40 close while switch arm 42 moves from contact 44 to contact 48 for connecting V to the control 50 for activating the pumps, such that they may be operated.

Referring now to FIG. 3, there is shown an exemplary embodiment of an encoding circuit for providing selectively the FIG. 2 wave forms. ON switch 52 is connected to OR circuit 54 which in turn is connected to input means 10. Input means may include a tone modulator and demodulator in a telephone communications network (not shown), such as is well known in the art. It is remembered that to turn equipment ON, tone signals AB must be simultaneously present for activating the amplifier 30 to switch relay 34 to its ON condition. ON switch 52 is therefore also connected to OR circuit 56 such that tone signals AB are simultaneously presented to input means 10 for so activating relay 34.

OFF switch 58 is depressed or closed for turning the equipment OFF from a remote site. It is connected to OR circuit 54 for continuously providing tone signal A so long as the switch 58 is closed. This closure corresponds to wave 12A of FIG. 2. Closure of switch 58 also activates delay circuit 60 which in turn sets monostable multivibrator 62 to its active condition. The active condition of monostable multivibrator 62 is indicated through OR circuit 56 to provide tone signal B to input means 10, corresponding to wave 14B of FIG. 2. Delay circuit 60 and monostable multivibrator 62 are respectively constructed similarly to delay circuit 18 and monostable multivibrator 24, as will be later described.

Inspection of FIG. 2 shows that wave 143 is initiated at a time subsequent to pulse 22A. Therefore, delay circuit 60 (FIG. 3) has a delay period greater than delay circuit 18 (FIG. 1) such that the tone B will be initiated at some time after monostable circuit 24 (FIG. 1) is set to its active condition. correspondingly monostable multivibrator 62 is set to its active condition, a time corresuonding to wave 14B which is shorter in duration than the time period provided by monostable multivibrator 24, indicated by waves 26A and 28A. This is important in turning the equipment OFF. If monostable multivibrator 62 had a time period extending beyond the time period of monostable multivibrator 24, the tone signal AB remains on line 32 (FIG. 1) after monostable 24 switched back to its inactive condition providing an activating voltage on line 28 to return relay 34 to its ON condition.

Referring now to FIG. 4 delay circuit 18 is shown as a unijunction transistor 64 RC charging threshold circuit. Capacitor 66 is charged by a voltage provided over line 16 through a suitable charging resistance. Upon charging to a predetermined positive voltage, unijunction transistor 64 switches to conduction supplying pulse 22A to coupling capacitor 68 to set monostable multivibrator 24. When tones A and B are simultaneously received before delay 18 period has expired, no pulse 22A is to be provided. To so prevent, a voltage indicating tones A and B is supplied over line 20 to delay circuit 18 for selectively clamping the unijunction circuit. The supplied voltage makes transistor 70 highly conductive to divert line 16 voltage from charging capacitor 66. It may be noted that tone B occurring any time before unijunction transistor 64 has switched its conductivity state from off to on, the delay circuit 18 will not provide O'FF indicating pulse 22A to monostable multivibrator.

Amplifier 30 consists of a pair of amplifying transistors 72 and 74 having their base electrodes respectively connected to line 28 and 26. Referring momentarily to FIG. 2 it is seen that wave 28A will keep transistor 72 conductive by being negative at all times except when monostable multivibrator 24 is set to its active condition. Transistor 72 being conductive will provide a low impedance path between isolation diode 76 which will pass positive tone signal B through transistor 72 over line 38 and thence the upper half of coil 78 to activate polar magnetic latching relay 34 to an ON condition. In a similar manner when monostable circuit 24 is set to its active condition wave 26A when switched to its low voltage value will activate transistor 74 to its active condition for passing tone signal B over line 36 to the lower half of coil 78 for activating relay 34 to the OFF state. Relay 34 may include noise suppression rectifiers 80 and 82, as shown.

What is claimed is:

1. A system for controlling the activation and deactivation of a two-state control device in accordance with the relative timing of first and second input terminals, which comprises:

(a) first and second system terminals for receiving first and second input signals respectively;

(b) a delay means having input, output and inhibit terminals, said input terminal being coupled to the first system terminal, said inhibit terminal being coupled to the second system terminal, said delay means providing an output signal after a predetermined interval in response to an input signal, the application of a signal at the inhibit terminal during said interval preventing an output signal from said circuit;

(c) monostable means having an input terminal coupled to the delay means output terminal and first and second output terminals, said means being triggered to its active state by a signal from said delay means whereby a signal is provided at said first output terminal, said means reverting to its inactive state after a predetermined period and providing a signal at its second output terminal;

((1) enabling means having first and second input terminals coupled to the first and second output terminals of said monostable means respectively, said means further having first and second output terminals and an enabling terminal, said enabling terminal being coupled to the second system terminal whereby a signal applied to said second system terminal both inhibits said delay means and enables said enabling means, the presence of a signal at said second system terminal providing a signal at one of said enabling means output terminals in accordance with the input signal at the corresponding input terminal of said enabling means, and

(e) means for coupling the first and second output terminals of said enabling means to said control device, the state of said control device being controlled by the output of said enabling means which is determined by the timing of the signals applied to the first and second system terminals.

2. The system of claim 1 wherein said delay means comprises:

(a) unijunction transistor having first, second and control electrodes, said first electrode being resistively coupled to a voltage supply, said second electrode being resistively coupled to a reference potential;

(b) means for coupling the second electrode of said unijunction transistor to the output terminal of said delay means;

(c) a charging resistor coupled between said delay means input terminal and said control electrode; (d) a capacitor coupled between said control electrode and a reference potential, the application of the first input signal at said first system terminal charging said capacitor to render said unijunction transistor conductive after a predetermined interval;

(e) a transistor having first, second and control electrodes, said first and second electrodes coupled to a reference potential and to the control electrode of said unijunction transistor respectively, the control electrode being coupled to the inhibit terminal of said delay means whereby the application of the second input signal to said second system terminal during said interval inhibits charging of said capacitor and prevents the unijunction transistor from becoming conductive.

3. The system of claim 1 wherein said enabling means comprises first and second transistors each having first, second and control electrodes, the first electrodes being coupled to the enabling terminal of said means, the second electrodes of said first and second transistors being coupled to said first and second output terminals respectively, the control electrodes of said first and second transistors being coupled to the first and second input terminals respectively,

the application of the second input signal to said enabling terminal providing an output signal at one output terminal in accordance with the signals applied to the enabling means input terminals.

References Cited UNITED STATES PATENTS 9/1955 Gordon et al 328120 4/1967 Huifman et al. 328120 US. Cl. X.R. 

